First, the basics: Common Core is a set of educational standards which tracks children's progress in math and English. Students in K-12 are tested every year on a set of rigorous of core concepts which are supposed to prepare kids for college and the workforce. (Via WCBS)

"Each stop is a chance for every parent and teacher to focus on the skills their student is supposed to know at that step. ... Each standard makes sure all students are learning what they need to know to get to graduation and beyond."

While a state's participation in Common Core isn't mandatory, the Obama administration has tied Common Core principles to the $4.35 billion Race To The Top educational grant. Forty-five states adopted Common Core standards when they were first announced.

In many ways, Common Core is a response to 2001's No Child Left Behind reforms, which evaluated schools based on student performance but let each state determine their own educational standards. In 2013, Education Secretary Arne Duncan told Politico that No Child Left Behind got things backwards.

"No Child Left Behind was very tight on means, but loose on goals. ... I'm trying to flip that on it's head. I want to have a high bar."

Proponents of Common Core, including Bill Gates and Florida governor Jeb Bush, argue tougher standards will inspire better curriculums and more graduates who are better equipped to compete in the job market. (Via C-SPAN, ABC)

But while Common Core sets the standards for education, it's up to the states to develop the curriculum which teaches these standards — and that's where the initiative runs into trouble.

Thousands of parents in New York are choosing not to have their children take the Common Core test this year, after schools posted abysmal test scores last year. Critics say the state's program is poorly implemented and focuses on test scores over education. (Via NY1)

And several prominent educators have blasted Common Core standards for evaluating teachers and administrators based on a single standardized test score. "Teachers across the country will be fired if the scores of their pupils do not go up. This is nuts." (Via The Washington Post)

The backlash against Common Core inspired Indiana's state legislature to pull out of the program and offer its own standards, and Oklahoma is considering similar measures.